Make usb storage disk recognisable by Windows XP

Sometimes your computer refuses to recognise usb flash disks or portable hard disk. I had this problem when I tried to connect my 160GB Western digital portable hard disk to my work computer. I could connect my 1GB usb flash disks and my computer would recognise it but not my portable hard disk. I thought that my company would have set rules on the size of hard disk that you can connect to the computer. One of my work mates told me to check the disk management and see if my hard disk is there. When I saw my hard disk listed there, I was confused. Then he told me to assign a different drive letter to my hard disk. When I did this my computer recognised my portable hard disk and I was able to access the files and folders in them.